In various industrial or commercial applications, an amount of current flowing through an electrical conductor may be measured using a current measuring device. One known current measuring device uses a core of magnetic material having an opening through which an electrical conductor passes, where the core of magnetic material is generally shaped as a toroid and defines a “slot-shaped” air gap, in which a Hall effect sensor is positioned. The slot-shaped air gap of the known current measuring device has a rectangular cross-sectional shape, and a three-dimensional shape of a box (e.g., a right rectangular prism). The current through the conductor contributes to a magnetic field within the toroid-shaped core of magnetic material. Magnetic flux lines through the core pass through the slot-shaped air gap, and are sensed by the Hall effect sensor that is positioned within the slot-shaped air gap. Flux density across the slot-shaped air gap may be proportional to the amount of current flowing through the conductor, and a determination of the current may be based on the flux density measured by the Hall effect sensor.
FIG. 1A is a conceptual diagram of such a prior art current sensor 10. A current-to-be-measured flows through a conductor 12. Conductor 12 passes through an opening 14 defined by a magnetic core 16 of magnetic material. Magnetic core 16 defines a slot-shaped air gap 18, in which a Hall effect sensor 20 is positioned to measure flux density of the magnetic field induced by the current flowing through the conductor 12. A determination of the current flowing through conductor 12 may be obtained based on the measured flux density.
As shown in FIG. 1A, slot-shaped air gap 18 is bounded from above and below, respectively, by a first face 22 of magnetic core 16 and by a second face 24 of magnetic core 16. Slot-shaped air gap 18 has a rectangular cross-sectional shape, and Hall effect sensor 20 is positioned approximately in the middle of slot-shaped air gap 18, roughly an equal distance from first face 22 as from second face 24. In three dimensions, slot-shaped air gap 18 generally has a “slot” or “box” shape. Slot-shaped air gap 18 is completely bounded on its top and bottom sides, respectively, by first face 22 and second face 24 of magnetic core 16.
FIG. 1B is a conceptual diagram of the slot-shaped air gap 18 defined by the magnetic core 16 of FIG. 1, showing magnetic flux lines 26 through the slot-shaped air gap 18. In general, the magnetic flux lines 26 flow around (not shown in FIG. 1B) the magnetic core 16, and as shown in FIG. 1B, flow across slot-shaped air gap 18 in a generally uniform manner between first face 22 and second face 24 of magnetic core 16. Because the separation between first face 22 and second face 24 is generally uniform across the slot-shaped air gap 18, reluctance (that is, resistance to flux flow) is generally uniform across the slot-shaped air gap, resulting in the generally uniform flux pattern across the air gap 18, as shown. For simplicity, Hall effect sensor 20 is not shown in FIG. 1B.